IROC_385Z

I'm pretty sure I have my own answer but I would really like for people to confirm or deny...

Its a 385 stroker, 3.75 with 6.0 rods and forged wiseco pistons (1/16 rings).

Upon startup it sounds like a Diesel and after it warms up it makes this chatter sound that I cannot tell where it comes from...below the manifold/valve covers.

THis is the first time I have run forgings and I don't know what sounds to expect from them. I understand that they must run looser in the bore due to more expansion. I also want to say that I have heard that long-rod stroker's will have more piston slap since the skirts are so small. I can only assume that these two traits are causing my noises.

If this is the case, what do you guys think that this would do to the long-gevity of the motor? Is there something I can do to quiet this (thicker oil?) or should I just accept it and not worry? I am kinda paranoid cause I just got this damn motor done, after a good year of B/S/T and $$...

All comments are welcome, Thanks.

IROC_385Z

Come on, some of you guys have to have some input here?

five7kid

iTrader: (14)

What kind of cam/lifters are you running? What kind of fuel pump? Does the noise sound like all the cylinders or only one?

I had a forged piston SBC in the 70's that chattered, but it also had a solid lifter cam. The noise didn't really change in the 4 years I had it (only car I had at the time).

IROC_385Z

Thanks for replying. I'm running a hyd roller with the in-tank pump...

The sound is hard to pinpoint...its just the "engine" making the noise, lol: It sounds like a freakin diesel motor sometime! I would say yes, all 8.

I'm running a quench of .044, is it possible for the pistons to be kissing the heads or do you think its just them rocking in the bores?

The guy who did all of my machine work and helped guide me along with this engine is a very reputable race-engine builder in the area. After I get it running I'm going to take it to him to see what he thinks, but I have a feeling that he will look at me like im a noob and say that he doesn't hear anything to worry about...kinda a goofy guy he is.

RB83L69

If it quiets down after it warms up, it's the pistons loose in the bores. Ignore it, it's normal. Above all, DON'T put thicker oil in it; that won't help anything, and may very well make it worse.

IROC_385Z

I suppose that this will wear out the rings/walls pretty quickly then?

RB83L69

No....

Forged pistons are fit looser in the bores, because the metal expands more with heat. So in order for them to have the right clearance when they're hot, they're loose when they're cold.

The cold part is normal. The rest of it, I have no idea; I'd have to hear it in person to be able to tell you what it is.

five7kid

iTrader: (14)

There are those who argue that forged pistons aren't as good for power because the extra skirt clearance required reduces ring sealing capability. However, forged pistons tend to last longer in higher power situations, so, it's the old trade-off thing.

I never noticed any ring degradation with the old SBC. I've been running forged pistons in the current 396 since 1997, beat them regularly on weekends, no problems thus far. And, interestingly, no piston slap noise like the SBC had, either.

IROC_385Z

Again, thanks for all your help guys.

The only thing I can think it may be is that I have (don't laugh) factory center-bolt valve covers installed while using Gold rollers...I put then on to stop a pesky oil leak while breaking it in and don't recall if the sound was there before I put them on or not.

I will be firing it up for the year this week and am ganna swap to taller covers and adjust the valves again (i think I used the 1/2 to 3/4 turn and am ganna reset them to 1/4 turn) to see that happens.

I'll let ya guys know how it goes.

THanks

IROC_385Z

Oh, and 5-7, what size rings were on that SBC?

five7kid

iTrader: (14)

Whew, no idea! That engine was put together in 1973 by someone who was a lot better at that stuff than I was (or am, likely). I can only assume they were stock sized.